Femtosecond-laser-encoded distributed-feedback color center laser in lithium fluoride single crystal

Focused infrared femtosecond laser pulses (wavelength ∼800 nm, emission pulse duration 100 fs) were employed to fabricate optoelectronic devices such as waveguides, micro-gratings and laser active centers in LiF crystals. F2 color centers of about 2 × 1018 cm−3 and refractive index change of about 1% at 633 nm were induced by the fs-laser irradiation. This technique was applied to fabricate a distributed-feedback (DFB) F2 color center laser structure inside LiF single crystal. The LiF DFB laser exhibited laser oscillation at 707 nm at room temperature. The slope efficiency of ∼10% and beam divergence of ∼20 mrad were achieved.